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| Detailed Reference Information |
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Forsythe, L.M., Nielsen, R.L. and Fisk, M.R. (1994). High-Field-Strength Element Partitioning between Pyroxene and Basaltic to Dacitic Magmas. Chemical Geology 117(1-4): 107-125. doi: 10.1016/0009-2541(94)90124-4. |
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The effects of composition and temperature on pyroxene-melt partitioning of the high-field-strength elements (HFSE) - Ti, Zr, Nb and Ta - were evaluated from doped experiments on natural mafic to intermediate composition lavas at pressures from 0.1 MPa to 0.9 GPa (0.001 to 9 kbar). The HFSE partition coefficients (D) maintain similar relative relationships: D-Ti > D-Zr > D-Ta > D-Nb, but vary absolutely as a function of composition and temperature, often exhibiting a range of over a factor of 5 at a single temperature. For example, D-Zr ranges from 0.1 in a tholeiitic melt to 0.6 for a dacitic melt at 1100 degrees C, 0.1 MPa. D-Zr, D-Ta, and D-Nb for high- and low-Ca pyroxene can be described as linear functions of D-Ti. For high-Ca pyroxenes, the functions are D-Zr=0.64D(Ti)-0.13, D-Ta=0.14D(Ti)-0.02 and D-Nb=0.04D(Ti)-0.01. The low-Ca pyroxene expressions are D-Zr=0.60D(Ti)-0.06, D-Ta=0.27D(Ti)-0.005 and D-Nb=0.08D(Ti)-0.005. This linear relationship suggests similar substitution mechanisms for Ti and the other HFSE in both pyroxene and silicate melts. An expression was derived to calculate the Ti content of pyroxene based on the melt composition, Ca content of the pyroxene, temperature and pressure. This expression uses an approximation of the equilibrium constant for an exchange reaction of a Ti/Al-bearing component with a Ca-bearing component in the pyroxene. Over the experimental temperature range (1170-1070 degrees C), the clinopyroxene Ti contents can be reproduced with a precision of +/-120% (1 sigma). |
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Abstract |
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Table 1 |
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Table 2 |
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Table 3A |
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Table 3B |
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Table 3C |
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Table 3D |
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Table 5 |
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Table 4 |
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Table 6 |
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Experiments |
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Microprobe Analysis |
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Equilibrium Test |
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Henry's Law |
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Keywords
rare-earth elements, distribution coefficients, silicate melts, plagioclase feldspar, kilauea volcano, trace-elements, ca pyroxene, arc basalts, henry law, sr |
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Publisher
Elsevier Science
P.O. Box 211
1000 AE Amsterdam
The Netherlands
(+31) 20 485 3757
(+31) 20 485 3432
nlinfo-f@elsevier.com |
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